1. Field of the Invention
The present invention relates to a touch sensor.
2. Discussion of the Related Art
Input of a touch sensor may include a driving signal input through a capacitance between a sensing electrode and a driving electrode of a touch panel, and a noise signal input through a capacitance between a sensing node of the touch panel and an object (e.g., a finger) touching the touch panel, and a sensed signal may be obtained by mixing two signals.
A sensor of a touch sensor detects variation in mutual capacitance, and a digital processor of the touch sensor processes the detected variation in mutual capacitance to produce a digital signal. The digital signal is provided to device firmware, which in turn performs calculations for extraction of x and y coordinates corresponding to the variation in mutual capacitance. The firmware may then transfer the coordinates to a host as final touch location information. The resolution of information produced by the digital processor may be a factor determining the accuracy of the coordinate calculation provided by the firmware.
In some circumstances, interference from sources external to the touch sensor may interfere with operation of the touch sensor. For example, nearby fluorescent lights or spurious signals from a charging device coupled to the touch sensor may interfere with output of the touch sensor. For example, such interference may cause the output of an amplifier (e.g., an operating amplifier) of an analog signal sensor of the touch sensor to be outside a normal operating range or an output waveform of the analog signal sensor may be distorted due to overlap with noise. Such interference may prevent normal transfer of information from the touch sensor.